What describes the gradual difference in concentration of a dissolved substance in a solution?

A concentration gradient is a fundamental concept in biology, describing the gradual change in the concentration of a dissolved substance across a space. This gradient is significant because it drives processes such as diffusion and osmosis. When there is a difference in concentration, molecules will naturally move from an area of higher concentration to an area of lower concentration in an attempt to achieve equilibrium.

In the context of cell biology, concentration gradients are crucial for functions like nutrient uptake, waste elimination, and maintaining homeostasis. For example, oxygen will diffuse from an area where its concentration is high (outside the cell) to an area where it is low (inside the cell), facilitating cellular respiration.

Other terms, like pH, proton gradient, and cohesion, refer to different concepts. pH measures the acidity or basicity of a solution. A proton gradient, specifically, refers to the difference in proton concentration across a membrane, often in the context of ATP production in cellular respiration. Cohesion describes the attraction between molecules of the same substance, such as water molecules. Thus, concentration gradient specifically captures the essence of the gradual difference in concentration of a dissolved substance.